Average Signal Level Research Articles

Real-Life In-Home Viewing Conditions for Flat Panel Displays and Statistical Characteristics of Broadcast Video Signal

The goal of this study is to clarify the realistic viewing conditions and video signal characteristics surrounding flat panel display television (TV), as flat panel display television is becoming increasingly popular. We have conducted an investigation of TV viewing conditions in the home and the statistical characteristics of TV broadcast signals. Our study of viewing conditions indicates that the viewing environment at home is at minimum 3 times of the absolute display height with an average 2.5 m viewing distance, a less than ±45° TV viewing angle, and a 100–300 lx mean screen illuminance. Our analysis of the broadcast signal indicates that the velocity for the motion of a picture of a general TV program is distributed below 20°/s, visible camera blur is seen when the motion speed is higher than 10°/s, and average signal levels of TV broadcast in Japan are at 40 and 25% for ASL and ALL levels, respectively.

Comparison of 900 and 1800 MHz Indoor Propagation Deterioration

The results of signal strength measurements and ray tracing model calculations of indoor propagation at 900 and 1800 MHz are presented. Corridors are being illuminated by ceiling mounted 2 dB gain omni antennas. The objectives of these experiments are to study behavior of the received signal strength at 900 and 1800 MHz in comparison of cell coverage, signal attenuation and variation through the line of sight (LOS) and non line of sight (NLOS) orientation of halls. It is shown that large fluctuations occur between average signal levels in LOS and NLOS case of propagation. It is also obtained that ray tracing model neglecting diffraction effects work better for LOS then NLOS, and requires detailed database information for better prediction

Characterisation of AlGaN MSM by Light Beam Induced Current technique

The influence of the grain structure on the performance of AlGaN MSM detector structures was examined by Light Beam Induced Current (LBIC) technique. LBIC is a mapping technique in which the generated photocurrent is measured for each position of the scanning light beam. Estimated values for the effective carrier collection regions between contact electrodes in AlGaN MSM structures are hundreds of nanometers. A non-uniformity of the carrier distribution was observed. Regions, where the measured signal was one order of magnitude larger than the average signal level, were also observed. LBIC method was applied for investigation of layer quality and for optimisation of MSM detectors. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Hearing aid with adaptive microphone matching

A method and apparatus for matching or balancing average signal levels between at least two input signal channels and their respective microphone elements so as to allow a hearing aid or instrument to maintain optimum directional characteristics over time are provided. The hearing aid may comprise an analogue signal processor or a digital signal processor adapted for controlling characteristics, e.g., gain and/or frequency response, of one or more of the input signal channels.

A wall imperfection channel model for signal level prediction and its impact on smart antenna systems for indoor infrastructure WLAN

This paper presents a novel approach for the estimation of the local average signal level in an indoor environment based on a wall imperfection model. A ray-tracing tool based on the method of images with angular information, is first used to estimate the distribution of field strength (or coverage) in an arbitrary environment. The concept of spatial sampling is highlighted. The wall imperfection model is then introduced to study the sensitivity of the received signal level at an arbitrary location to imperfect wall positioning and electromagnetic material properties. An alternative approach to estimate the local mean signal level at a particular point is presented based on the wall imperfection model to reduce the computation time. The impact of the wall imperfection model on the patterns of a smart antenna system serving multiple users in an infrastructure WLAN is studied.

Characterization of radio wave propagation into buildings at 1800 MHz

The paper presents the results of signal strength measurements at 1800 MHz in four office buildings in The Hague, illuminated by an outdoor base station with an antenna above the rooftop. The objectives of these experiments are to study the behavior of the received signal strength at different floors of a building and to determine the main characteristics concerning cell coverage, namely, signal attenuation and variation within these buildings. It is shown that large fluctuations occur between average signal levels in line-of-sight (LOS) and non-LOS areas of multifloor buildings.

Coding of amplitude-modulated signals in the cochlear nucleus of a grass frog

To study the mechanisms that govern the coding of temporal features of complex sound signals, responses of single neurons located in the dorsal nucleus of the medulla oblongata (the cochlear nucleus) of a curarized grass frog (Rana temporaria) to pure tone bursts and amplitude modulated tone bursts with a modulation frequency of 20 Hz and modulation depths of 10 and 80% were recorded. The carrier frequency was equal to the characteristic frequency of a neuron, the average signal level was 20–30 dB above the threshold, and the signal duration was equal to ten full modulation periods. Of the 133 neurons studied, 129 neurons responded to 80% modulated tone bursts by discharges that were phase-locked with the envelope waveform. At this modulation depth, the best phase locking was observed for neurons with the phasic type of response to tone bursts. For tonic neurons with low characteristic frequencies, along with the reproduction of the modulation, phase locking with the carrier frequency of the signal was observed. At 10% amplitude modulation, phasic neurons usually responded to only the onset of a tone burst. Almost all tonic units showed a tendency to reproduce the envelope, although the efficiency of the reproduction was low, and for half of these neurons, it was below the reliability limit. Some neurons exhibited a more efficient reproduction of the weak modulation. For almost half of the neurons, a reliable improvement was observed in the phase locking of the response during the tone burst presentation (from the first to the tenth modulation period). The cooperative histogram of a set of neurons responding to 10% modulated tone bursts within narrow ranges of frequencies and intensities retains the information on the dynamics of the envelope variation. The data are compared with the results obtained from the study of the responses to similar signals in the acoustic midbrain center of the same object and also with the psychophysical effect of a differential sensitivity increase in the process of adaptation.

Electro-optically modulated polarizing Fourier-transform spectrometer for plasma spectroscopy applications.

A new electro-optically modulated optical solid-state (MOSS) interferometer has been constructed for measurement of quantities related to the low-order spectral moments of line emission from optically thin radiant media such as plasmas. When Doppler broadening is dominant, the spectral moments give the Radon transform of corresponding moments of the velocity distribution function of the radiating species. The instrument, which is based on the principle of the Fourier-transform spectrometer, has high etendue and is rugged and compact. When electro-optical path-length modulation techniques are employed, the spectral information is encoded in the temporal frequency domain at harmonics of the modulation frequency and can be obtained by use of a single photodetector. Specifically, for a plasma in drifting local thermodynamic equilibrium the zeroth moment (brightness) is given by the average signal level, the first moment (shift) by the interferometric phase, and the second moment (linewidth) by the fringe visibility. To illustrate the MOSS performance, I present spectroscopic measurements of the time evolution of the plasma ion temperature and flow velocity for rf-heated discharges in the H-1 heliac, a toroidal plasma magnetic confinement at the Australian National University.

Modulated optical solid-state spectrometer applications in plasma diagnostics

A new electro-optically modulated optical solid-state (MOSS) interferometer has been constructed for the measurement of the low order spectral moments of line emission from optically thin radiant media. The instrument, which is based on the principle of the Fourier transform spectrometer, is rugged, compact, and inexpensive and offers a number of advantages over conventional grating based spectrometers. Most importantly, by employing electro-optical path-length modulation techniques, the spectral information is obtained using a single photomultiplier tube. Specifically, the zeroth moment (brightness) is given by the average signal level, the first moment (shift) by the modulation phase and the second moment (line width) by the modulation amplitude. In applications such as Zeeman spectroscopy and motional Stark effect (MSE), polarization modulation can be used to effect a modulation of the center frequency and/or coherence of the light which is then measured by the MOSS spectrometer. This article describes a number of applications, including Doppler and charge exchange recombination spectroscopy and polarization spectroscopy (Zeeman and MSE) for which the MOSS spectrometer is an inexpensive and powerful alternative to multichannel grating spectrometers.

DNA strand separation studied by single molecule force measurements

We have separately attached the two complementary strands of one end of a DNA double helix to a glass slide and a glass microneedle. Displacing the slide away from the needle, the molecule is progressively pulled open and the changing deflection of the needle gives the corresponding variation in the opening force. Force signals which are very rich in detail are reproducibly obtained. The average level and amplitude of the force signal is almost independent of the opening velocity in the interval 20 nm/s to 800 nm/s. A theoretical description based on the assumption of thermal equilibrium allows us to link the measured force curves to the genomic sequence of the DNA. A molecular stick-slip motion is revealed, which in contrast to the dynamics of macroscopic solid friction is a deterministic and reproducible process. This process is considered experimentally and theoretically.

A Standardized Approach to Collecting and Calculating Noise Amplitude Spectra

A standardized approach to acquire, calculate, and display noise spectra is proposed. The method is based on normalizing the noise amplitude spectrum to the average dc level of the input signal. This normalization procedure should allow noise spectra, obtained in different laboratories or from different sources, to be compared both quantitatively and qualitatively. A review of the proper techniques to acquire and compute noise spectra is also given.

Voice activity detector for speech signals in variable background noise

A voice activity detector (VAD) which determines whether received voice signal samples contain speech by deriving parameters measuring short term time domain characteristics of the input signal, including the average signal level and the absolute value of any change in average signal level, and comparing the derived parameter values with corresponding thresholds, which are periodically monitored and updated to reflect changes in the level of background noise, thereby minimizing clipping and false alarms.

Conference system with automatic speaker detection and speaker unit

A conference system comprises speaker units (12) coupled to a central unit (14). The speaker unit (12) comprises an echo canceller (20) with an adaptive filter (38) having an impulse response of comparatively short duration. In a speech pause of the user of the speaker unit (12) the common listening signal (LS) of the conference system is applied to the loudspeaker (18). Of the sounds then picked up by the microphone (16) only those sounds are compensated which are produced by the loudspeaker (18) and which reach the microphone (16) directly and which reach the microphone (16) indirectly via reflections from nearby objects. These sounds have a comparatively short impulse response time and enable a comparatively simple adaptive filter (38) to be used. The other sounds picked up by the microphone (16) reach the microphone (16) via reflections from the walls of the conference space (10) in which the conference system is situated. The other sounds have a comparatively long impulse response time. For the purpose of automatic speech detection these other sounds do not require echo cancellation because they are the same for all the speaker units. Automatic speech detection is now accomplished if the signal strength of the compensated microphone signal (MCCS) produced by the echo canceller (20) exceeds the average signal level of the speaker units.

On-vehicle audio system reproducing bodily sensible sounds

An on-vehicle audio system reproducing bodily-sensible sounds is devised to rapidly eliminate masking of bodily-acoustic audio sounds caused by vibrations of a running vehicle and generate bodily-sensible sounds without giving an inharmonious feeling to the listener. The system has a low pass filter for extracting only low frequency band components of an input signal, an amplifier for amplifying the output of the low pass filter and delivering the amplified signal, a vibration unit disposed in a seat of the vehicle for converting the amplified signal to mechanical vibrations. To eliminate the masking, the system is provided with a vibration sensor for generating a vibration signal of a magnitude in accordance with vibrations of the vehicle, and a level adjusting unit for adjusting the level of the input signal in accordance with an average level of the vibration signal.

Experimental research on the statistical characteristics of radar signal spikes at small grazing angles

The results of research into the characteristics of spikes in a radar signal scattered by the sea surface at small grazing angles and horizontal polarization of radiation are reported. Studies were carried out at wind speeds of 4.4–10.3 m s−1. It is shown that the experimental distribution of the amplitudes of the radar signal spikes is described well by an exponential function. The distribution of the amplitudes of spikes, normalized to their average value for the measurement cycle, is of universal character. It does not depend on the observational conditions. The relationship between the average level of signal and the wind speed agrees with the results of computation on the model suggested.

Significance of skin temperature changes in surface electromyography

Differing results have been reported concerning the direction and quantity of the electromyogram (EMG) amplitude response to changes in tissue temperature. The EMG signals from the soleus muscle of six healthy human subjects were therefore recorded during dynamic exercise (concentric contractions) at ambient temperatures of 30 degrees C and 14 degrees C. The mean skin temperature (Tsk) above the muscle investigated was 32.9 degrees C and 21.7 degrees C, respectively. The core temperature, estimated by rectal temperature, was unchanged. The cooling of the superficial tissues caused approximately a doubling of the EMG amplitude. For the probability level 0.9 in the amplitude probability distribution function, the average signal level increased from 73 microV to 135 microV (P = 0.02). The average mean power frequency of the EMG signal was reduced from 142 Hz to 83 Hz (P = 0.004). The amplitude increase was not due to shivering but other possible explanations are presented. As the changes in Tsk investigated were within the range which may occur normally during the working hours, it was concluded that Tsk should be carefully controlled in vocational EMG studies.

Acoustic emission during the deformation of α-lactose monohydrate and anhydrous α-lactose monocrystals

During the deformation of single crystals of alpha-lactose monohydrate and anhydrous alpha-lactose in a crushing strength rig, their acoustic activity was monitored using a portable activity meter. The acoustic parameters measured were the average signal level (ASL), count rates and total acoustic counts. Both types of lactose, even though deformed by fragmentation, differed fundamentally in the degree and nature of this fragmentation. Close correlation was observed between the ASL, count rate profiles and the force-displacement profiles. The monohydrate form is acoustically more active than the anhydrous form during deformation. Small internal fractures which were neither visually observed nor detected in the force-displacement profiles (in particular the anhydrous alpha-lactose) were detected by monitoring the acoustic signals during the deformation of these crystals. This work illustrates the potential of using the acoustic emission technique as an aid in the assessment of the deformation characteristics of pharmaceutical materials during single crystal compression studies.

Effects of semiconductor-optical-amplifier nonlinearity on the performance of high-speed intensity-modulation lightwave systems

It is shown that when the amplifier is driven near saturation, its inherent nonlinearity causes significant bit-pattern-dependent pulse distortion, particularly in the bit-rate range between about 2 and 32 GB/s. Without proper countermeasures, this distortion can degrade system performance appreciably due to two basic mechanisms. The first, which can result in a system power penalty of as much as 10 dB, occurs in a standard decision circuit that automatically sets the threshold voltage to the average signal level, rather than in the middle of the eye opening. The second mechanism, which occurs even with the threshold set properly, is due to the nonlinear enhancement of the simple linear intersymbol interference (ISI) within the receiver filter. For example, computations of system performance at 8 Gb/s using an RC filter that gives a quite acceptable 10% of eye closure under linear conditions show that when the amplifier is driven to its saturation output power level, this mechanism causes a system power penalty of about 1 dB, which increases to about 4.5 dB when the power is doubled. Interestingly, with the proper threshold setting, an ideal integrate-and-dump receiver, which introduces no ISI, is shown to suffer no power penalty due to amplifier nonlinearity.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Measurements of 800-MHz Radio Transmission Into Buildings With Metallic Walls

In this paper we describe an experiment conducted to measure 800-MHz attenuation into buildings. This information is needed for refining the configuration and design of portable radiotelephone systems that will accommodate low-power portable sets. Signal levels have been measured in and around three small buildings and a house, using an instrumentation van with an erectable 27-foot-high antenna. These buildings and the house all have metallic materials in their walls and thus are expected to exhibit high attenuation. The van was parked at one location with respect to the three buildings, and at nine different locations, at distances ranging from 400 feet to 1600 feet, from the house. We found that small-scale signal envelope variations are approximately Rayleigh distributed. For the house, large-scale distributions of the small-scale signal medians are approximately log-normal. Median signal levels outside the house decrease as d <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−4.5</sup> , where d is the distance from the van. Inside the house, levels decrease as d <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3.9</sup> for first-floor locations and as d <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3.0</sup> for second-floor locations. Average signal levels at 1000 feet, relative to free space, are −12.5 dB outside, −18.5 dB for the first floor, −16.5 dB for the second floor, and −28.9 dB for the basement. Other statistics of the signal levels and of attenuation into the house are also given in the paper. Cross-polarization couplings of −10 dB to 0 dB were measured in and around the three small buildings. The small-scale signal medians inside the three buildings range from 2 dB above to 24 dB below the averages of the signal medians outside buildings.

Microwave propagation measurements for mobile digital radio application

Measurements over a variety of urban and terrain conditions were made using a spread-spectrum waveform centered at 1370 MHz. Chip rates of 10 and 20 MHz were used, giving high time-delay resolution. The transmitter end of the measurement link was elevated and fixed while the receiver was mobile. A detailed analysis of the multipath structure was made for various terrain conditions. This included distributions of the number and spacing of individual multi-path components as a function of amplitude threshold and also distribution of total delay. Thresholds are referenced to both average signal level and the maximum level in each pulse interval. Some instances of spatial variation of the received signal are also presented.